riscv: remove unused functions in traps_misaligned.c

Replace macros by the only two function calls that are done from this
file, store_u8() and load_u8().

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Link: https://lore.kernel.org/r/20231004151405.521596-2-cleger@rivosinc.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>